1. Filed Of The Invention
The present invention relates to a directing device, for feeding, selecting and sorting objects, of the type having a series of planar conveying devices pulled along a fixed path and able to unload objects carried thereon at predetermined unloading stations. Each conveying device has a small, rotary, planar-belt, object-carrying conveyor powered by an electric motor, preferably D.C. A special characteristic of the device according to the invention is the possibility of controlling each small belt conveyor independently of all the others and in a manner commanding belt rotation in one or the other direction at a selected speed, as unloading requires. Another characteristic of the device according to the invention is that the conveying devices can move along paths curving in horizontal or vertical planes.
2. Description Of The Prior Art
Directing devices are well known, such as those used in large post offices to sort mail, or in mail order companies, or wherever there is a need to select and distribute a large number of products which can differ in bulk, weight, and collection point. Some of these devices consist of continuous-belt conveyors with deviators or similar devices therealong controlled by electromechanical devices to unload objects carried on the continuous-belt conveyors. Other devices consist of a series of platforms carried along a fixed path and interactive with devices which cause them to tilt for the unloading operation as required.
These known devices have substantial limitations. Some cannot follow irregular paths. Others unload all the objects carried in the same way, which is a big operational limitation.
In the latter case, for example, where the device serves a number of machine tools, the limitation is especially substantial. Each machine tool has to be fed objects at a quite specific rhythm according to the machining operation the machine tool performs, and as a consequence, the workpieces must reach the machine tools at intervals which differ from machine tool to machine tool. Consequently, for example, separate belt conveyors have been used to carry workpieces to respective machine tools at different intervals, preferably correlated to the speed of the belt itself.
The utility of a device that permits objects to be unloaded at different intervals, depending on the unloading station, or even at the same station, therefore appears clear.
There are brochures illustrating directing-device systems produced by the ALVEY, CRISPLANT, LOGAN AND TISSMETAL T.L.D. companies. The market for directing-device systems is quite limited and, among the therefore-non-numerous companies supplying this market, those cited above are most representative.
The system produced by ALVEY is made up of a roller conveying surface along a fixed path. At unloading stations, the conveying surface is crossed, transversely, by mechanically-operated pushers, for discharging roller-conveyed objects.
The system produced by CRISPLANT is made up of a series of small, object-carrying tilting trays down along a fixed path. As they pass an unloading station, the tilting trays are mechanically tilted by an electromagnetically-controlled cam.
The system produced by LOGAN is made up of object-carrying tilting trays drawn along a fixed path and tilted by an electro-pneumatic cam.
The system produced by TISSMETAL T.L.D. is made up of a series of small, object-carrying tilting trays on two tilting frames drawn along a fixed path. An electro-pneumatic device actuates one of the two tilting frames of each tray.
The former thus utilize tilting trays or a continuous conveyance surface as conveyed elements, and not small rotating belts. The latter feature, together with the adoption of permanent-magnet D.C. motors could provide remarkable advantages, especially due to the high speed and acceleration performances of the motors, particularly if controlled by a computer. With suitable sensors (photoelectric cells), it would be possible to check the position of the items to be discharged continuously and with maximum precision and, therefore, to operate the system members (i.e. the motored small rotating belts), via a computer, with high performance. The system members could discharge items at a high speed to make it possible to adopt sorting windows (i.e. unloading stations) of minimum dimensions and to place them side by side, thus attaining considerable space-saving and the ability to handle a larger number of items. This cannot be obtained with the above-described mechanically-operated systems of the prior art due to the acceleration and speed requirements, which cannot be met due to the need to reduce wear and tear on their systems.
U.S. Pat. No. 3,912,071 discloses a sorting system in which each of a series of item conveyors has a small rotating belt for mechanical operation by devices at the discharging points (i.e. unloading stations).
The patent also considers the possibility of operating the small rotating belts with electric motors on carrier units of the item conveyors. The kind of motor is not specified, however, and the patent does not suggest the use of permanent magnet D.C. motors.